LOS ANGELES - Harry Burkhart watched as his mother was arrested last week on fraud charges from their native Germany, and a day later he exploded in an expletive-laced rant against America at her US court hearing following her arrest on a provisional warrant.

The next day, police say, the 24-year-old began a nighttime rampage of arson attacks that terrorized Los Angeles.

Authorities have yet to disclose why they believe that the pony-tailed, 24-year-old Hollywood resident set the fires, but his mother’s legal trouble provides one glimpse into the turmoil in his life.

Court documents unsealed yesterday said Dorothee Burkhart, who is in her 50s, was charged with 19 counts of fraud in Frankfurt, including failing to pay for a 2004 breast-augmentation surgery and pilfering security deposits from renters.

Outside his Hollywood apartment, some neighbors described him as a loner who loitered around the busy commercial strip at night and could be heard arguing with his mother.

But Shlomo Elady, a hair stylist who regularly trimmed Burkhart’s long hair, recalled someone who spoke three languages, dreamed of visiting Jerusalem, and cared for a sickly mother who had trouble walking.

Elady said he was stunned that the man who lived with his mother above his Sunset Boulevard shop is suspected of torching vehicles, some just steps from his home. The fires caused an estimated $3 million in damage.

“He loved his mom, the way every son loves his mom,’’ Elady said. “He’s not a creepy guy.’’

Burkhart was taken into custody after authorities received a tip from federal officials who recognized him in a security video that showed a pony-tailed man emerging from a garage where a car was set ablaze.

“When they saw the security footage, they recognized him and they contacted the arson task force,’’ a State Department official told the Associated Press, speaking on condition of anonymity because the investigations are ongoing.

The official didn’t know the mother’s immigration status or what type of visas the pair used to enter the country. As German citizens, they would be eligible to come to the United States without a visa for 90 days under the Visa Waiver Program.

A federal law enforcement official, speaking on condition of anonymity because the official was not authorized to discuss the case, said Harry Burkhart was present when his mother was arrested Dec. 28 on a provisional arrest warrant.

Provisional arrest warrants are normally issued when there are criminal charges pending overseas against someone. Ordinarily, US authorities then obtain an arrest warrant through the State Department and the Justice Department.

While the mother was in court Thursday afternoon, Harry Burkhart launched into an obscenity-laden tirade, saying “[Expletive] the United States!’’ said Thom Mrozek, spokesman at the US Attorney’s office in Los Angeles.

Mrozek said Burkhart was detained and later escorted out of the courthouse. He said Burkhart did not make any specific threats against anyone or property at his mother’s court hearing.

Galina Illarionova, who lives in the same apartment complex as the suspect, said through a Russian translator that an agitated Burkhart visited her Sunday and said his mother was having some kind of legal problems.

He told her his mother was in trouble with authorities and wanted Illarionova to attend a legal hearing with him, but he later said he didn’t need her help.

A domain name for a website offering appointment-only sensual massage is registered to Dorothee Burkhart. Her name is not mentioned on the website, which states the service is not prostitution.

The series of fires appeared to have stopped with Burkhart’s arrest. The onslaught of intentionally set fires kept residents anxious over the holiday weekend.

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